Fluorescent lighting system



Dec. 22, 1959 L. LEITZ 2,918,567

FLUORESCENT LIGHTING SYSTEM Filed Sept. 18, 1957 2 Sheets-Sheet 1INVENTOR. Luow/g Le/fz 0 TM r' Dec. 22, 1959 -rz 2,918,567

FLUORESCENT LIGHTING SYSTEM Filed Sept. 18. 1957 2 Sheets-Sheet 2 Fig. 4

INVENTOR. L udw/g L e/fz Alforngy;

United States Patent FLUORESCENT LIGHTING SYSTEM Ludwig Leitz, Wetzlar,Germany, assignor to Ernst Leitz G.m.b.H., Wetzlar-Lahn, GermanyApplication September 18, 1957, Serial No. 684,730 Claims priority,application Germany September 19, 1956 5 Claims. (Cl. 240-9) The presentinvention relates to lighting equipment. More in particular, the presentinvention relates to elongated, tubular fluorescent lamps withpreferably planar reflectors and accompanying means for shielding theeye of the observer from glare effects of the light source.

It is known in the art to equip fluorescent lamps of the commercialelongated tubular type with means designed to protect the unshielded eyeof the observer from the glare effect of the lamp or its image. Sincethe conventional reflectors with which fluorescent lamps are generallyequipped afford only a partial and an insufiicient' protection,protective devices have been developed consisting of an array oflouvres, the latter being usually composed of an assembly of metal orplastic sheets. These anti-dazzle grids are usually vertically disposedrelative to the longitudinal axis of the lamp tube, and are positionedeither underneath the latter or underneath the reflectors, sometimes ina number of parallel rows, so as to form a grid shaped structure withthe reflectors. Their size is so designed that only diffused light isspread outside of the pyramid defined by the undiffused light raysemitted by the lamp.

It is also known to provide the louvres with a nonspecular surface. Inthis case the space free from glare elfects can be kept within a certainangular sector in the direction of the tube depending upon the distanceand the size of the metal or plastic sheets of the louvres. However, thelight rays are diffusedly reflected by the non-specular surface of themetal or plastic sheets and are therefore lost for lighting purposes. Onthe other hand, if the surfaces of the louvres are specular, the spacefree from dazzle effects cannot be determined at will. The product ofthe entrance aperture and the size of the entrance opening is equal tothe product of the exit aperture and the size of the entrance opening.Where the louvre sheets are arranged parallel to each other and theentrance opening is equal to the exit opening, and where the entranceaperture is 180 due to the longitudinal extension of the tube the exitaperture will also be 180, i.e. there will be a radiation in an angularsection of 180. An unconcentrated radiation of this kind is, of course,undesirable for practically all lighting purposes.

It is therefore an object of the present invention to provide a lightingequipment comprising tubular fluorescent lamps which assures a uniformand angular distribution of light within the desired area ofillumination and which eliminates undesirable and disturbing glareeffects.

It is another object of the present invention to provide a lightingequipment comprising tubular fluorescent lamps and reflectors associatedtherewith in which undesirable glare effects can be eliminated within apredetermined accurately' defined area and which simultaneously utilizesthe light rays emitted by the lamp tube to the greatest possible extentfor the purpose of illuminating a desired area.

These objects are achieved by the novel construction of my inventionwhich is based on my discovery that a particular shape and position ofthe reflectors relative to the position of the tubular fluorescent lampis suf ficient to assure the elimination of undesirable glare and dazzleeffects without requiring special anti-dazzle devices and arrangements,while utilizing to the fullest possible extent the light rays emitted bythe lamp for the illumination of the desired area.

According to my invention the fluorescent lamp construction is sodesigned that reflector walls situated on both sides of and parallel tothe lamp tube contact with their respective lower edges planesconstituting the bonu daries between light and shadow. Furthermore,these planes are tilted relative to the horizontal plane at an angle acorresponding to the desired range of absence of glare or dazzle effectsand the planes are finally tan gential to that part of the lamp tubewhich faces the floor. In addition, the walls of the reflectors mustform with the horizontal plane an angle ,8 which is equal to or smallerthan 90oc.

According to another embodiment of the present invention there areprovided reflector means which are transversely disposed relative to thelongitudinal axes of the lamp tubes and which have a V-shaped crosssection seen in transverse direction towards the longitudinal extensionof the tube. V-shaped reflectors are known but it was consideredimpossible to provide V-shapedreflectors transversely to the tube as itwas assumed that such a large area of the tubes was covered that theresulting loss of useful light would outweigh any advantage of such anarrangement. The present invention has overcome this prejudice. Becauseof the V- shaped construction of these transverse reflectors the exitopening is greater than the entrance opening and the range of radiationis smaller than 180.

The invention will be better understood upon the following descriptionof the accompanying drawings, wherein.

Figure 1 is a perspective view of the lighting equipment of the presentinvention;

Figure 2 is a somewhat schematic, cross sectional view of thefluorescent lamp tubes and the longitudinally extending reflectors inthe lighting equipment of the present invention;

Figure 3 is another somewhat schematic view, partly in longitudinalsection of the arrangement of the trans verse reflectors of theinvention;

Figure 4 is a diagram illustrating the relation of the angles v and 5;

Figure 5 is a cross sectional view of a transverse reflector of theinvention; 1

Figure 6 is a cross sectional view of a transverse reflector of theinvention having a cover.

Turning now to the drawings more in detail the lamp tubes 1 haveassociated reflectors 2. The respective lower edges of the walls 2a and2b of these reflectors 2 contact imaginary planes 4- which constitutethe boundaries between the light and shadow regions. The pianes 4 areinclined relative to the horizontal plane 5 at an angle a and they arearranged tangentially relative to the lower portions of the tubes 1facing the floor. The angle a defines the range free from dazzle orglare effects and it is chosen in correspondance with the desiredextension of that range. In the example shown in Figure l the angle a is30. The walls 2a and 2b of the reflectors have an inclination relativeto the horizontal plane 5 defined by an angle B. The ratio of the anglesa and B is so chosen that the virtual image of the tube remains alwaysabove the tangential plane 4 limiting the space free from glare ordazzle effects. The angle 6 has a maximum value of a or a value inferiorto 90 u.. As a result, if the eye of the observer looks in the direc-qtion of the fluorescent tubes at an angle smaller than 18, neither thetube nor a reflected image of the tube can be seen. In the example shownin Figure 2, the angle 3 defining'the inclination of the walls 2a and 2bof the reflectors 2 relative to the horizontal plane has a value of 60(90 x, i.e. 9030=60).

It should be kept in mind that the angle of inclination shown in theexample of Figure 1 must be regarded as a marginal value constitutingthe minimum inclination of the reflector walls 2a and 212 towards thehori- Zontal plane 5, defined by a maximum angle 5. In this marginalcase, the reflector surfaces have the smallest possible extension andthe total height of the lamp construction attains a minimum value. Ifthe angle of in clination of the reflectors towards the horizontal ismade smaller (which can be done to a certain marginal value) the lightyield can be increased. There will be, however, as an accompanyingresult, an undesirable influence upon the size of the reflecting surfaceand of the lamp construction which are both increased, since both thereflector surface and the lamp construction will have a greaterextension.

It has been discovered that the best overall results are obtained if acompromise is chosen between the greatest light yield and the minimumsize of the reflector surfaces and the lamp construction. According tothis solution only a certain portion of the reflector walls is arrangedat an angle of inclination, smaller than the aforemen tioned maximumvalue of the angle [5. For example, the reflector walls 241 and 2b canbe bent in the area neighboring the lamp tubes and preferably orrespective starting from the points of intersection 9a and 9b with thetangential planes 4 limiting the space free from glare so as to haveupper portions 2a, 2b, and lower, inwardly bent portions 2a", 2b, withthe upper portions 2a" and 2b" being inclined towards the horizontalplane 5 at an angle 18 which is inferior to 90a whereas the lowerportions 2a and'2b" are inclined towards the horizontal plane 5 at anangle having the maximum value of 90u (in the example shown in Figure 2,60).

In order to keep the total width of the lamp as small as possible it isfurther advisable to have the upper edges of the reflector wallsapproach the tube as much as possible, at a height correspondingapproximately to the longitudinal center line of the lamp. In doing sothat region of the lamp tube which is ordinarily prevented fromspreading useful light rays by the own shadow of the lamp is fullyutilized for illuminating the ceiling, from where the light may again bemore or less perfectly reflected to the lower parts of the respectiveroom, according to the condition of the ceiling.

According to a further advantageous feature of the present invention anassembly of tubular fluorescent lamps comprising at least two tubes isprovided with combined reflectors composed of one single V-shaped piece2 and disposed between two neighboring tubes. The single V-shaped piecethus provides one reflector Wall 2a for each of the two adjoining tubes,and, another reflector 'wall 2b for the other of the two adjoining lamptubes. Furthermore, there is provided a second set of reflectors 6(Figure 3) vertically and transversely arranged relative to thelongitudinal axis of the lamp tube replacing the conventional louvres oranti-dazzle grid structures. These vertical reflectors fulfill thedouble function of preventing a glare or dazzle etiect and at the sametime reflect the light rays emitted by the light source, i.e. with thefluorescent lamp tube thus contributing to a better utilization of thelight rays emanating from the latter. To accomplish these ends thevertically and transversely arranged reflectors 6 are so positioned thatthe light rays emitted by the light source and reaching the reflectingsurface of the transverse reflectors are reflected against the floor,thereby avoiding any glare or dazzle effect undesirable and unpleasantto the eye of the. observer. The transverse reflectors 6 are arrangedout of contact but very close to the lower side of the lamp tube 1. Theupper edges 60 of each of the transverse reflectors as well as the loweredges 6d of each neighboring transverse reflector contact imaginaryplanes '7 which are inclined towards the horizontal plane 5 at an angle7 which corresponds to the desired extension of the space which is freefrom glare or dazzle eflects.

In addition, the transverse reflectors are V-shaped and their lateralsides 6a and 6b form with the horizontal plane 5 and angle 6 which is Inthe example shown in Figure 3, the imaginary planes '7 are inclinedtowards the horizontal plane 5 at an angle =25, and the sides on and 6bof the transverse reflectors 6 are inclined towards the horizontal plane5 at an angle 6:77 30'.

An angle 7 of 30 has proved to be of particular ad vantage since in thatcase a maximum light yield is obtained while the overall size of thelighting equipment. is as small as possible. However, good results arealso obtained if the angle is a little smaller or wider by an amount of10, i.e. up to 40 and down to 20.

The width of the angle 6 should be smaller than constitutes the marginalwidth of the angle 6 in which there is no dazzling effect and in whichthe reflected rays.- are utilized to their fullest extent in the desiredarea which is to be illuminated. If the angle 6 is smaller than theintensity of the illumination is increased whereas the extension of theilluminated area is reduced.

The angles 7 and 6 will become apparent upon regarding Figure 4. Themarginal light ray A runs parallel to the longitudinal extension of lamptubes 1 and is reflected by the reflector 6a so as to be tangential tothe lower edge of reflector 6b and thus passing reflector 6b, since thereflector surface B of reflector 6a is vertically disposed relative tothe angle by sector C of the angles 7' and 'y with 7' being equal to 7.If the angle between the light ray A and the reflector surface, B of thereflector 6a is designated as e the following equations are valid:

The transverse reflectors 6 can be provided with a cover 8 protectingthe reflector from dust. The cover can be bulged in outward direction soas to have a con! vex configuration as shown in Figure 3 and may have aspecular surface 8c so as to undiflusedly reflect the light rays emittedfrom the fluorescent tube 1.

The cover can also have an angular configuration 8b as shown in Figure6.

The reflector walls 2a, 2b and 6a, 6b can be composed of a perfectly orpartly specular material. The respective upper ends 2c, 2d of thereflector walls 2a and 2b catilbe flanged to give suflicient stabilityto the reflector: wa s.

It will be understood that. this invention is-susceptible" tomodification in order to adapt it to different usages and conditions,and, accordingly, it is desired to com-- prehend such modificationswithin this invention as mayfall within the scope of the appendedclaims.

What I claim is:

l. Ina lighting equipment comprising a plurality of fluorescent lamptubes; longitudinal reflector means comprising a plurality oflongitudinally extending walls disposed on both longitudinal sides ofeach of said lamp tubes and parallel thereto, every two of said wallsintermediate two of said lamp tubes being composed of one V-shapedpiece, said reflector walls having lower edges adjoining an imaginaryplane defining the boundaries between light and shadow, said imaginaryplane being inclined towards the horizontal plane at a predeterminedangle a corresponding to the desired extension of space free from glareeffects and being tangential with the lower downwardly extending portionof said lamp, said reflector walls being bent at their point ofintersection with said imaginary plane so as to have an upper and alower portion above and below said bend, respectively, the respectivelower portions of said reflector walls being inclined towards thehorizontal plane at an angle inferior to 90 x, and a plurality oftransverse reflectors having reflector walls vertically extendingrelative to the longitudinal axes of said lamp tubes, the respectiveupper edges of said transverse reflectors and the respective lower edgesof the neighboring vertically extending reflectors adjoining animaginary plane which is inclined towards the horizontal plane at apredetermined angle 7 corresponding to the desired extension of spacefree from glare effects.

2. A lighting equipment as described in claim 1 wherein said transversereflectors are V-shaped and have two lateral surfaces which are inclinedtowards the horizontal plane at a predetermined angle 6 that is lessthan 3. A lighting equipment as described in claim 2, fur- 6 thercomprising an outwardly bulged cover placed on top of said V-shapedvertically extending reflectors.

4. A lighting equipment as described in. claim 2, further comprising anoutwardly bulged cover placed on top of said V-shaped verticallyextending reflectors, said cover having a specular surface.

5. A reflector arrangement for use with a lighting fixture having atleast one elongated light source, said arrangement comprising, incombination, longitudinal reflector means arranged on both longitudinalsides of said light source and being parallel thereto, said longitudinalreflector means flaring downwardly from said light source and havingupper edges which are at substantially the same level as the middle ofsaid light source; and transverse reflector means arranged between saidlongitudinal reflector means and extending upwardly to the region of thelowermost edge of said light source, said reflector means being in theform of wedge-shaped members which in a vertical plane of said lightsource have a downwardly tapering V-shaped cross-section, each memberbeing closed by an upwardly bulging cover element which is near saidlowermost edge of said light source and which has a specular outersurface.

References Cited in the file of this patent UNITED STATES PATENTS2,323,073 Netting June 29, 1943 2,337,437 Allen Dec. 21, 1943 2,436,635De Bishop Feb. 24, 1948 2,506,951 Doane May 9, 1950 2,615,123 Guth Oct.21, 1952 2,683,799 Taylor et al. July 13, 1954

